Cellular imaging has become more then ever an essential part of any project in the field of Cell Biology. As new proteins are identified there is increasinglly a need to apply morphological techniques to identify their localization and function. We are therefore requesting support for this Core so that we can continue providing essential support to all the projects associated with this PPG grant application. The Core will assist aft PPG members in experiments methods and analysis that is needed for advanced cellular imaging, with special emphasis on the high spatial and temporag resolution instruments needed for studies of membrane trafficking. New imaging microscooes including a 4D muIticolor deconvolution microscope and a confocal microscope fitted with cross-correlation fluorescence correlation spectroscopy (CC-FCS) have recently been acquired and will be used by the Core At the light microscopy level, we will take advantage of the new biological probes (e.g. GFP variants) and single molecule techniques that are rapidly expanding the power of cellular imaging in riving cells. At the electron microscopy level, we will continue to emphasize immunocytochemical localization of antigens on frozen thin sections and stereotogy as a way to determine the intracellular distribution of proteins at steady state or under various experimental or pathological conditions.